LOS ANGELES -- Nanny McPhee, a dark yet delicious children's movie, deals boldly with an age-old question in parenting: What do you do with naughty children?

In life, writer-actress Emma Thompson admits she does not have a clue. She even confesses to falling into a total emotional collapse when wrestling with the demons which occasionally inhabit her own spirited daughter, six-year-old Gaia (whom she shares with second husband, actor Grey Wise).

"Generally speaking," Thompson says with a laugh, "I often will end up weeping on the floor saying, 'I don't know how to discipline you! I don't know what to do now!'

"And my daughter has come up to me, looked at me weeping, sitting on the floor, given me a hankie and said, 'Let's have a game of cards.' I've also taught her how to make Bloody Marys now, so she knows kind of how to calm me down and it's all right now. Actually, in all seriousness, I think it's very difficult to know (what to do)."

In the movies, however, Thompson's title character in Nanny McPhee has some answers. They involve magic but also rely on human ingenuity, a child's cleverness and simple but forthright communication between generations.

Thompson says there is also one truth that unites the seven very naughty Brown children in the movie and most naughty children in real life. "Parents always think it's the kids' fault. If they're naughty, it's the kids' fault. Not true! Children generally are not naughty for no reason."

Those reasons, she says, usually involve an adult who does something, says something or ignores the children when they do and say things that demand close attention. Naughtiness is a child's protest against a perceived injustice, Thompson says. So acting out is sometimes a good thing.

As a result, Nanny McPhee, which combines the light-hearted spirit of Mary Poppins with the Gothic sensibilities of a Grimm fairytale, is a cautionary saga, equally powerful for naughty children and for their parents.

"I think it would be terrible if what children come away (with) from this movie was that you've always got to behave," Thompson says. "No! Not so!"

Set during the Dickensian-Victorian era in a small English town, the movie has been spun from Christianna Brand's three books on the exploits of Nurse Matilda. Generally lost and forgotten, they are now being republished under the combined title Nanny McPhee: The Collected Tales Of Nurse Matilda. The new volume is comprised of Nurse Matilda (1964), Nurse Matilda Goes To Town (1967) and Nurse Matilda Goes To Hospital (1974).

Thompson, who won an Oscar for adapting Jane Austen's classic novel, Sense And Sensibility, into an Ang Lee masterpiece, wrote the screenplay for Nanny McPhee. She was also the one to get the project going -- nine years ago.

"It was an odd genesis," Thompson says. "I read (one of the Nurse Matilda books) when I was little but it wasn't one of my favourites. But I was dusting, actually, and I found it on the bookshelves. I looked at this strange little dumpy woman on the front, with this huge tooth, and I thought, 'I remember this book and I think her appearance changes.' As I read it (again), I thought, 'There's something about this that might make a good film.' "

Thompson took the idea to producer friend Lindsay Doran. The two met on set in 1990 when Thompson shot Dead Again with her then-husband, actor-director Kenneth Branagh. Doran was keen and the two embarked on what proved to be -- surprisingly -- a very difficult journey.

"I thought, of course because I'm an idiot," Thompson says, "that writing something like that would be simpler than adapting a major movie. Wrong! In fact, it was more difficult because there is, in fact, not a narrative in the books. I suddenly discovered that I agreed to write this thing and there wasn't a story. So I had to make a lot of it up. Well, all of it up, really!"

For example, Thompson killed off Mrs. Brown and turned Mr. Brown (played by Colin Firth) into a widower. There is also the question of the exact number of Brown siblings, but we will get to that in a moment. The few servants in service in the Brown household also changed and so did their importance. In the movie, a scullery maid (Kelly Macdonald) figures into the romantic plot in a crucial way while Mr. Brown's rich, imperious aunt (Angela Lansbury) makes key demands that threaten to ruin his life. But the consequences could be dire if Mr. Brown refuses her because her financial support maintains the household.

Consequently, Nanny McPhee the movie bears little resemblance to Nurse Matilda the books. Except that each shares writer Brand's original vision: That the nanny who cares for the Brown children has magical powers and deep insight into what makes children tick. She also has two large warts, a bulbous nose and a snaggle tooth, as Brand writes, "sticking right out like a tombstone over her lower lip." Ugly, ugly!

As for the children themselves, there are oodles of them in the books, running around, causing mayhem, getting into mischief. As Brand writes on Page 1 of Nurse Matilda, "There were so many of them that I shan't even tell you their names but leave you to sort them out as you go along."

Thompson says she was forced to, as screenwriter, "kill a lot of the children because they had so many kids in the books. You can't count them. My first version of this film had 35 kids in it. Can you imagine? Slowly, as the years went by, Lindsay ground me down. She said, 'We can't have 35 children! It's too expensive.' "

Thompson's stubborn response? "Okay, I'll give you 29! Then I slowly went down to 17, 13, 11 and nine. I absolutely stopped at nine. I said, 'I'm not going to do any less than nine. It's not going to make enough sense. It's not going to be enough kids.' So we ended up with seven."

Seven turned out to be a magical number (and the filmmakers needed eight to play them, with twins Hebe and Zinnia Barnes as Baby Agatha). "Actually," Thompson says, "I was watching The Sound Of Music the other day and it's seven. Robert Wise did rather well with that film because they're (all seven children) quite well documented."

What was good enough for Wise is good enough for her, Thompson says. "I realized I couldn't chart nine kids in an hour and a half. It just wasn't going to be possible."

What was equally challenging was the makeup. Thompson arrives with a most excellent freak look as Nanny McPhee. Her visage evolves toward the 46-year-old Thompson's own natural beauty, as she teaches her lessons. Warts vanish, the nose shrinks, the tooth decays away.

"From a continuity point of view," director Kirk Jones says, "it really was quite a complex shoot. It was complicated in the children's hours, as well. With the makeup, handling the children and the schooling, you really had to look at it almost as a military operation. There were charts and lists and we had to mark out every single day."

Just as complex is the mythology behind the story, Thompson says. "It's fascinating, actually. I really ought to research it more because, when I started to work out what myth Nanny McPhee was, I realized she was more like Shane than anything else (a reference to the 1953 classic Hollywood western in which a stranger, Alan Ladd, arrives at a settler's home and transforms a boy's life before riding off into the desert).

"That myth, that story form," Thompson says, "is probably very ancient and it is to do with chaos. It is to do with a situation where chaos reigns and all the powers that be and the authorities that are existent cannot do anything. They cannot act, they cannot restore balance or harmony. (Then) a stranger comes in -- indeed, (Albert) Camus' La Peste is the same thing -- and restores balance or harmony or order and then has to leave or die. They cannot stay. That's the interesting thing about it. They have to go."

Kids were fine, but the ass was a real pain

There is an old adage in Hollywood that adult actors should never work with children or animals.

"I don't think that is true," says Emma Thompson, writer and star of the movie Nanny McPhee, "although you should never work with donkeys!"

Let's talk children first. Even though they are referred to as "dreadful, awful, monstrous creatures" in the press materials for the film, that is written with great affection. And Thompson got along famously with all eight children playing the seven offspring of Mr. Brown in the movie.

Indeed, as she leaves her Hollywood interview sessions one recent day, she spies young Samuel Honywood -- an extraordinarily articulate youngster who plays Sebastian -- and chases him about until, catching up, she bundles him into her arms for a big hug. Both squeal in delight.

Thompson also got along with the various animals on set for the English shoot in Buckinghamshire and at famed Pinewood Studios. The menagerie included a big pig dressed up in Sunday finery. But that damned donkey!

"That donkey was supposed to be active," Thompson says. "And it just stood there as if it had been injected with half a pound of heroin. You know that thing they say at the end of movies -- 'No animal was harmed, accidentally or otherwise' ... well, I wanted to harm it. I wanted the end of (the movie) to say, 'Emma Thompson harmed the donkey!' Because I had a real, profound desire. That's a terrible thing to admit but there you go."